Classifications

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  • A61B5/369—Electroencephalography [EEG]
  • A61B5/377—Electroencephalography [EEG] using evoked responses
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  • A61B3/0016—Operational features thereof
  • A61B3/0025—Operational features thereof characterised by electronic signal processing, e.g. eye models
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  • A61B3/02—Subjective types, i.e. testing apparatus requiring the active assistance of the patient
  • A61B3/024—Subjective types, i.e. testing apparatus requiring the active assistance of the patient for determining the visual field, e.g. perimeter types
• • A—HUMAN NECESSITIES
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  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/113—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for determining or recording eye movement
• • A—HUMAN NECESSITIES
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  • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/14—Arrangements specially adapted for eye photography
  • A61B3/145—Arrangements specially adapted for eye photography by video means
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/16—Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state
  • A61B5/161—Flicker fusion testing
• • A—HUMAN NECESSITIES
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  • A61B5/16—Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state
  • A61B5/163—Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state by tracking eye movement, gaze, or pupil change
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/25—Bioelectric electrodes therefor
  • A61B5/279—Bioelectric electrodes therefor specially adapted for particular uses
  • A61B5/291—Bioelectric electrodes therefor specially adapted for particular uses for electroencephalography [EEG]
• • A—HUMAN NECESSITIES
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• • A—HUMAN NECESSITIES
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  • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
  • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
  • A61B5/6802—Sensor mounted on worn items
  • A61B5/6803—Head-worn items, e.g. helmets, masks, headphones or goggles

Definitions

• This patent document relates to systems, devices, and processes that use brain machine interface (BMI) technologies.
• BMI brain machine interface
• Electroencephalography is the recording of electrical activity exhibited by the brain using electrodes positioned on a subject's scalp, forming a spectral content of neural signal oscillations that comprise an EEG data set.
• the electrical activity of the brain that is detected by EEG techniques can include voltage fluctuations, e.g., resulting from ionic current flows within the neurons of the brain.
• EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, e.g., less than an hour.
• EEG can be used in clinical diagnostic applications including epilepsy, coma, encephalopathies, brain death, and other diseases and defects, as well as in studies of sleep and sleep disorders. In some instances, EEG has been used for the diagnosis of tumors, stroke and other focal brain disorders
• EEG electroencephalogram
• mfSSVEP multifocal steady-state visual-evoked potentials
• the disclosed techniques integrate mfSSVEPs into a portable platform using wireless EEG and a head mounted display, demonstrating ability to assess potential visual field deficits, e.g., in conditions such as glaucoma.
• a system for monitoring brain activity associated with visual field of a user includes a sensor unit to acquire electroencephalogram (EEG) signals including one or more electrodes attached to a casing wearable on the head of a user; visual display unit including a display screen to present visual stimuli to the user in a plurality of sectors of a visual field, in which the presented visual stimuli includes an optical flickering effect at a selected frequency mapped to each sector of the visual field, the visual stimuli configured to evoke multifocal steady-state visual-evoked potentials (mfSSVEP) in the EEG signals exhibited by the user acquired by the sensor unit; and a data processing unit in
• a method for examining a visual field of a subject includes presenting, to a subject, visual stimuli in a plurality of sectors of a visual field of a subject, in which for each sector the presented visual stimuli includes an optical flickering effect at a selected frequency; acquiring electroencephalogram (EEG) signals from one or more electrodes in contact with the head of the subject; processing the acquired EEG signals to extract multifocal steady-state visual-evoked potentials (mfSSVEP) data associated with the subject's EEG signal response to the presented visual stimuli; and producing a quantitative assessment of the visual field of the subject based on the MfSSVEP data.
• EEG electroencephalogram
• mfSSVEP multifocal steady-state visual-evoked potentials
• a portable system for monitoring brain activity associated with visual field of a user includes a brain signal sensor device to acquire electroencephalogram (EEG) signals including one or more electrodes attached to a casing wearable on the head of a user; a wearable visual display unit to present visual stimuli to the user and structured to include a display screen and a casing able to secure to the head of the user, in which the wearable visual display is operable to present the visual stimuli in a plurality of sectors of the user's visual field, such that for each sector the presented visual stimuli includes an optical flickering effect at a selected frequency, and in which the visual stimuli are configured to evoke multifocal steady-state visual-evoked potentials (mfSSVEP) in the EEG signals exhibited by the user acquired by the brain signal sensor device; a data processing unit in communication with the brain signal sensor device and the wearable visual display unit to provide the visual stimuli to the wearable visual display unit and to analyze the acquired EEG signals and produce an assessment of the user
• EEG electroencephal
• the disclosed portable platform for assessing functional loss can facilitate detection and monitoring of visual field loss in glaucoma, the leading cause of blindness in the world.
• the disclosed portable platform uses high-density EEG recording and mfSSVEP that can provide improved signal-to-noise ratios, increasing reproducibility and diagnostic accuracy, e.g., as compared to existing EEG-based methods for objective perimetry, such as mfVEP.
• the disclosed methods can allow for much broader and more frequent testing of patients, e.g., as compared to existing perimetric approaches. For example, this could reduce the number of office visits necessary for patients at risk or diagnosed with glaucoma, significantly decreasing the economic burden of the disease.
• the disclosed methods can facilitate the discrimination of true deterioration from test-retest variability, e.g., resulting in earlier diagnosis and detection of progression.
• the disclosed portably-implemented and objective methods for visual field assessment can also allow screening for visual loss in underserved populations.
• the disclosed technology is non-invasive and can be implemented without direct physical contact with an eye of the individual subject being assessed, and thereby avoid causing any discomfort or risk of injury through inadvertent application of force or transfer of harmful chemical or biological material to the eye.
• FIG. 1A shows a diagram of an exemplary system to implement the techniques of the disclosed technology.
• FIGS. IB-IE show diagrams of an exemplary method to examine visual field defects using the disclosed technology.
• FIG. IF shows diagrams depicting an exemplary implementation using multifocal steady-state visual-evoked potentials (mfSSVEP) for assessment of visual field defects.
• mfSSVEP multifocal steady-state visual-evoked potentials
• FIG. 2 shows images of an exemplary EEG setup used in exemplary
• FIG. 3A shows data plots depicting exemplary CONTROL-DEFICIT
• FIG. 3B shows data plots depicting a BLOCK-CONTROL comparison in mfSSVEP profiles from a representative subject.
• FIG. 4 shows an image of an exemplary portable device of the disclosed portable, objective mfSSVEP -based visual field assessment platform.
• FIGS. 5A and 5B show images of an exemplary wearable, wireless 64-channel dry EEG system.
• FIGS. 6A and 6B show an image and a diagram of an exemplary head-mounted display system and presentation layout to present an exemplary mfSSVEP stimulation, respectively.
• Optic neuropathy refers to optic nerve damage that can result in significant and irreversible loss of visual function and disability.
• glaucoma is associated with a progressive degeneration of retinal ganglion cells (RGCs) and their axons, resulting in a characteristic appearance of the optic disc and a concomitant pattern of visual field loss.
• RRCs retinal ganglion cells
• Loss of visual function in glaucoma is generally irreversible, and without adequate treatment the disease can progress to disability and blindness. The disease can remain relatively asymptomatic until late stages and, therefore, early detection and monitoring of functional damage is paramount to prevent functional impairment and blindness.
• glaucoma affects more than 70 million individuals worldwide with approximately 10% being bilaterally blind, which makes it the leading cause of irreversible blindness in the world.
• the disease can remain asymptomatic until it is severe, the number of affected individuals is likely to be much larger than the number known to have it.
• Population-level survey data indicate that only 10% to 50% of the individuals are aware they have glaucoma.
• Visual dysfunction appears to be a strong predictor of cognitive dysfunction in subject in a number of clinical neuroscience disorders.
• the functional deficits of glaucoma and Alzheimer's Disease include loss in low spatial frequency ranges in contrast sensitivity, and are similar in both diseases.
• Pattern masking has been found to be a good predictor of cognitive performance in numerous standard cognitive tests. Some tests found to correlate with pattern masking include Gollin, Stroop-Work, WAIS-PA, Stroop-Color, Geo- Complex Copy, Stroop-Mixed and RCPM, for example.
• Losses in contrast sensitivity at the lowest spatial frequency also was predictive of cognitive losses in the seven tests. For example, AD subjects have abnormal word reading thresholds corresponding to their severity of cognitive impairment and reduced contrast sensitivity in all spatial frequencies as compared to normal subjects.
• SAP standard automated perimetry
• Visual field assessment with SAP requires considerable subjective input from the patient, and for some patients it is very difficult, or even impossible, to obtain reliable visual field measures.
• SAP is also limited by large test-retest variability and a large number of tests are usually necessary in order to discriminate true disease progression from noise, even for reliable test-takers.
• SAP testing is limited by subjectivity of patient responses and large variability, frequently requiring a large number of tests for effective detection of change over time. These tests are generally conducted in clinic -based settings and, due to limited patient availability and health care resources, an insufficient number of tests are frequently acquired over time, resulting in delayed diagnosis and detection of disease progression.
• the requirements for highly trained technicians, cost, complexity, and lack of portability of SAP testing also preclude its use for screening of visual field loss in
• Neurological disorders e.g., such as macular degeneration, diabetic retinopathy, optic neuritis, papilledema, anterior ischemic optic neuropathy, and tumor, can be diagnosed and tracked by SAP.
• VEP visual evoked potential
• multifocal VEP techniques have been limited by relatively low signal to noise ratio and have shown limited potential to assess visual field losses in the disease.
• the conventional pattern VEP is predominantly generated by cortical elements receiving projections from the central retina, where the central 2° of visual field contributes 65% of the response. Therefore, conventional VEP possesses a limited ability to reflect field loss in non-central areas, such as those that can occur with glaucoma.
• VEP techniques cab allow many areas of the retina to be stimulated simultaneously and separate responses from each part of the visual field to be obtained, individual differences in the anatomy of the visual cortex lead to considerable inter-individual variability of responses in normal subjects, making it difficult the identification of mfVEP abnormalities in diseased patients.
• existing mfVEP recording techniques can only be performed with non-portable devices in clinic- or laboratory-based settings, requiring cumbersome setup for placement of electrodes (e.g., data collection requires skin preparation and gel application to ensure good electrical conductivity between sensor and skin), and such procedures are time consuming and uncomfortable for the patient.
• the present technology includes methods, systems, and devices that acquire, process, and/or utilize steady-state visually evoked potentials (SSVEP) for monitoring, tracking, and/or diagnosing various paradigms in cognitive function (e.g., visual attention, binocular rivalry, working memory, and brain rhythms) and clinical neuroscience (e.g., aging, neurodegenerative disorders, schizophrenia, ophthalmic pathologies, migraine, autism, depression, anxiety, stress, and epilepsy), particularly for SSVEPs generated by optical stimuli.
• cognitive function e.g., visual attention, binocular rivalry, working memory, and brain rhythms
• clinical neuroscience e.g., aging, neurodegenerative disorders, schizophrenia, ophthalmic pathologies, migraine, autism, depression, anxiety, stress, and epilepsy
• EEG electroencephalogram
• the disclosed techniques integrate mfSSVEPs into a portable platform using wireless EEG and a head mounted display capable of assessing potential visual field deficits.
• the disclosed technology can be applied to diagnose and track neurological disorders, e.g., such as macular degeneration, diabetic retinopathy, optic neuritis, papilledema, anterior ischemic optic neuropathy, and/or tumors.
• the present technology utilizes rapid flickering stimulation to produce a brain response characterized by a "quasi-sinusoidal" waveform whose frequency components are constant in amplitude and phase, e.g., the so-called steady - state response.
• the portable platform integrates a wearable, wireless, high-density dry EEG system and a head-mounted display allowing users to routinely monitor the electrical brain activity associated with visual field stimulation.
• the present technology includes brain-computer interfaces using dry EEG sensor arrays, wearable/wireless data acquisition and signal processing hardware and software. These interfaces can monitor and record non-invasive, high spatiotemporal resolution brain activity of unconstrained, actively engaged human subjects.
• the disclosed technology can be applied for ophthalmologic diagnosis of neurological complications, in particular that of major ocular pathologies including glaucoma, retinal anomalies and of sight, retinal degeneration of the retinal structure and macular degeneration, diabetic retinopathy, optic neuritis, optical neuroma, or degenerative diseases, e.g., such as Parkinson's disease, Alzheimer's disease, non-Alzheimer's dementia, multiple sclerosis, ALS, head trauma, diabetes, or other cognitive disorders, e.g., such as dyslexia. More broadly, the present technology can be used to characterize inappropriate responses to contrast sensitivity patterns, and disorders affecting the optical nerve and the visual cortex.
• degenerative diseases e.g., such as Parkinson's disease, Alzheimer's disease, non-Alzheimer's dementia, multiple sclerosis, ALS, head trauma, diabetes, or other cognitive disorders, e.g., such as dyslexia.
• the present technology can be used to characterize inappropriate responses to contrast sensitivity patterns,
• MS multiple sclerosis
• the disclosed technology includes portable platforms that can be used for accurate and convenient screening of many neuro-degenerative diseases, e.g., including Alzheimer's, non-Alzheimer's dementia, Parkinson's, multiple sclerosis, macular degeneration, ALS, diabetes, dyslexia, head trauma, and others.
• neuro-degenerative diseases e.g., including Alzheimer's, non-Alzheimer's dementia, Parkinson's, multiple sclerosis, macular degeneration, ALS, diabetes, dyslexia, head trauma, and others.
• the present technology utilizes electroencephalogram (EEG)-based brain sensing methods, systems, and devices for visual-field examination by using high-density EEG to associate the dynamics of multifocal steady-state visual-evoked potentials (mfSSVEP) with visual field defects, in which the use of rapid flickering stimulation can produce a brain response characterized by a "quasi-sinusoidal" waveform whose frequency components are constant in amplitude and phase, the so-called steady-state response.
• EEG electroencephalogram
• mfSSVEP is a form of steady-state visual-evoked potentials which reflect a frequency -tagged oscillatory EEG activity modulated by the frequency of periodic visual simulation higher than 6 Hz.
• the mfSSVEP is a signal of multi-frequency tagged SSVEP, e.g., which can be elicited by simultaneously presenting multiple continuous, repetitive black/white reversing visual patches flickering at different frequencies.
• a flicker sector(s) corresponding to a visual field deficit(s) will be less perceivable or unperceivable and thereby will elicit a weaker SSVEP, e.g., as compared to the brain responses to other visual stimuli presented at normal visual spots.
• the disclosed methods, systems, and devices for visual-field examination using mfSSVEP data includes the formation of a spatial visual stimulus display having multiple regions or sectors at different spatial locations, where for each region, the particular region includes an optical effect (e.g., light flickering) that changes at a unique frequency with respect to at least a proximate region or any other region of the visual stimulus display.
• the visual stimulus display can include twenty regions each presenting its respective optical effect at a different frequency between 8.0 Hz and 1 1.8 Hz (e.g., 8.0 in sector 1, 8.2 in sector 2, 8.4 in sector 3, ..., 1 1.8 in sector 20).
• the optical effect can be a light modulating between an ON and OFF state at the designated frequency for the particular region.
• the brain response to the visual stimuli e.g., as measured by at least one electrode placed on or near the head or multiple electrodes arranged in an arrangement to improve spatiotemporal resolution of the EEG signals, are acquired and processed to produce and evaluate mfSSVEP data with respect to a frequency spectrum including the designated frequencies mapped to the spatial regions of the visual stimulus display.
• the processing includes comparing the mfSSVEP signal at the particular frequencies to a predetermined threshold, or in relation to other mfSSVEP signals, to determine if the signal falls below the predetermined threshold or is substantially lower with respect to a comparative mfSSVEP signal.
• Determination of a mfSSVEP signal below the threshold or substantially lower than a standard at that particular frequency corresponds to a visual field deficiency to the spatial location on the visual stimulus display to which that frequency is mapped, and indicative of a visual field defect of the user in that specific region.
• the disclosed techniques include using SSVEP and brain-computer interfaces (BCIs) to bridge the human brain with computers or external devices.
• BCIs brain-computer interfaces
• the users of SSVEP -based brain-computer interface can interact with or control external devices and/or environments through gazing at distinct frequency-coded targets.
• the SSVEP -based BCI can provide a promising communication carrier for patients with disabilities due to its high signal-to-noise ratio over the visual cortex, which can be measured by EEG at the parieto-occipital region noninvasively.
• Methods, devices and systems of the disclosed technology can implement wireless SSVEP data acquisition and processing.
• Methods, devices and systems of the disclosed technology can include a noninvasive platform for continuously monitoring high temporal resolution brain dynamics without requiring conductive gels applied to the scalp.
• An exemplary system can employ dry microelectromechanical system EEG sensors, low-power signal acquisition, amplification and digitization, wireless telemetry, and real-time processing.
• the present technology can include analytical techniques, such as independent component analysis, which can improve detectability of SSVEP signals.
• mfSSVEP multifocal techniques to SSVEP
• mfSSVEP multifocal techniques to SSVEP
• the exemplary results of such implementations demonstrate detection of localized and peripheral field losses, as well as show successful implementations of a portable objective method of assessment of visual field loss in opto-neurological diseases, e.g., such as glaucoma, amblyopia, age-related macular degeneration, and optic neuritis.
• the exemplary visual field assessment methods can be used for screening in remote locations or for monitoring patients with the disease in underserved areas, as well as for use in the assessment of visual field deficits in other conditions.
• the disclosed technology includes a portable platform that integrates a wearable, wireless EEG dry system and a head-mounted display system that allows users to routinely and continuously monitor the electrical brain activity associated with visual field in their living environments, e.g., representing a transformative way of monitoring disease progression, e.g., such as in glaucoma.
• Such devices provide an innovative and potentially useful way of screening for the disease.
• the disclosed technology includes portable brain-computer interfaces and methods for sophisticated analysis of EEG data, e.g., including capabilities for diagnosis and detection of disease progression.
• the disclosed methods, systems, and devices can be implemented to improve screening, diagnosis and detection of disease progression and also enhance understanding of how the disease affects the visual pathways.
• FIG. 1A shows a diagram of an exemplary portable EEG-based system 100 of the disclosed technology to implement the methods described in this patent document.
• the EEG- based system 100 integrates a wearable, wireless, high-density dry EEG sensor unit 1 1 1 and a visual display unit 1 12 (e.g., such as a head-mounted display) in data communication with a data processing unit 120 allowing users to routinely monitor the electrical brain activity associated with visual field stimulation.
• the data processing unit 120 can include various modules or units of the disclosed system for processing data extracted from the subject, e.g., via the EEG unit 1 11, based on stimulus of the subject via the visual display unit 112.
• the visual display unit 1 12 can include an output unit that can include various types of display, speaker, and/or printing interfaces, e.g., which can be used to implement a visual stimulus technique.
• the output unit can include cathode ray tube (CRT), light emitting diode (LED), or liquid crystal display (LCD) monitor or screen, among other visual displays, as a visual display.
• the output unit can include various types of audio signal transducer apparatuses or other sensory inducing apparatuses to implement the sensory stimuli.
• the data processing unit 120 can include a processor 121 that can be in communication with an input/output (LO) unit 122, an output unit 123, and a memory unit 124.
• the data processing unit 120 can be implemented as one of various data processing systems, such as a personal computer (PC), laptop, and mobile communication device.
• the data processing unit 120 can be included in the device structure that includes the wearable EEG sensor unit 1 11.
• the processor 121 can be included to interface with and control operations of other components of the data processing unit 120, such as the I/O unit 122, the output unit 123, and the memory unit 124.
• the memory unit 124 can store information and data, e.g., such as instructions, software, values, images, and other data processed or referenced by the processor 121.
• RAM Random Access Memory
• ROM Read Only Memory
• Flash Memory devices and other suitable storage media can be used to implement storage functions of the memory unit 124.
• the memory unit 124 can store data and information, which can include subject stimulus and response data, and information about other units of the system, e.g., including the EEG sensor unit 1 1 1 and the visual display unit 112, such as device system parameters and hardware constraints.
• the memory unit 124 can store data and information that can be used to implement the portable EEG -based system 100.
• the I/O unit 122 can be connected to an external interface, source of data storage, or display device.
• Various types of wired or wireless interfaces compatible with typical data communication standards can be used in communications of the data processing unit 120 with the EEG sensor unit 1 11 and the visual display unit 112 and/or other units of the system, e.g., including, but not limited to, Universal Serial Bus (USB), IEEE 1394 (FireWire), Bluetooth, IEEE 802.1 11 , Wireless Local Area Network (WLAN), Wireless Personal Area Network (WPAN), Wireless Wide Area Network (WWAN), WiMAX, IEEE 802.16
• the I/O unit 122 can interface with an external interface, source of data storage, or display device to retrieve and transfer data and information that can be processed by the processor 121, stored in the memory unit 124, or exhibited on the output unit 123.
• the I/O unit 122 can interface with an external interface, source of data storage, or display device to retrieve and transfer data and information that can be processed by the processor 121, stored in the memory unit 124, or exhibited on the output unit 123.
• the data processing unit 120 can include an output unit 123 that can be used to exhibit data implemented by the data processing unit 120.
• the output unit 123 can include various types of display, speaker, or printing interfaces to implement the output unit 123.
• the output unit 123 can include cathode ray tube (CRT), light emitting diode (LED), or liquid crystal display (LCD) monitor or screen as a visual display to implement the output unit 123.
• CTR cathode ray tube
• LED light emitting diode
• LCD liquid crystal display
• the output unit 123 can include toner, liquid inkjet, solid ink, dye sublimation, inkless (e.g., such as thermal or UV) printing apparatuses to implement the output unit 123; the output unit 123 can include various types of audio signal transducer apparatuses to implement the output unit 123.
• the output unit 123 can exhibit data and information, such as the system data in a completely processed or partially processed form.
• the output unit 123 can store data and information used to implement the disclosed techniques.
• FIG. 1A also shows a block diagram of the processor 121 that can include a central processing unit (CPU) 125 and/or a graphic processing unit (GPU) 126, or both the CPU 125 and the GPU 126.
• the CPU 125 and GPU 126 can interface with and control operations of other components of the data processing unit 120, such as the I/O unit 122, the output unit 123, and the memory unit 124.
• FIG. IB shows a diagram of an exemplary method 180 to examine visual field defects using the disclosed technology, e.g., such as including the system 100.
• the method 180 includes a process 182 to present, to a subject, visual stimuli in a plurality of sectors of a visual field of a subject, in which for each sector the presented visual stimuli includes an optical effect (e.g., light flickering) at a selected frequency.
• the method 180 includes a process 184 to acquire EEG signals from one or more electrodes in contact with the head of the subject.
• the method 180 includes a process 186 to data process (e.g., analyze) the acquired EEG signals to extract mfSSVEP data associated with the subject's EEG signal response to the presented visual stimuli.
• the method 180 includes a process 188 to produce a quantitative assessment of the visual field of the subject based on the MfSSVEP data.
• the quantitative assessment produced by the process 188 can provide an indication if there is a presence of a visual field defect in the user's visual field.
• the process 188 can include a process to determine the presence of the visual field defect in a sector having a mfSSVEP signal below a predetermined threshold.
• the visual stimuli presented by the process 182 can include multiple and repetitive optical effects flickering at the selected frequency in the corresponding sector of the visual field of the subject.
• the process 182 includes a process 181 to provide the visual stimuli to the visual display unit 112 (e.g., including a wearable visual display unit) from the data processing unit 120, in which the providing can include generating the visual stimuli (e.g., produce and/or assign an optical flickering effect of the visual stimuli at a selected frequency associated with each sector of the visual field); and/or supplying a previously generated visual stimuli.
• the visual display unit 112 e.g., including a wearable visual display unit
• the providing can include generating the visual stimuli (e.g., produce and/or assign an optical flickering effect of the visual stimuli at a selected frequency associated with each sector of the visual field); and/or supplying a previously generated visual stimuli.
• the process 181 to provide the visual stimuli includes forming a spatial visual stimulus display having multiple regions or sectors at different spatial locations, where for each region, the particular region includes an optical effect (e.g., light flickering) that changes at a unique frequency with respect to at least a proximate region or any other region of the visual stimulus display.
• an optical effect e.g., light flickering
• the process 188 can include a process 189 to analyze the mfSSVEP data with respect to a frequency spectrum including the designated frequencies mapped to the spatial regions of the visual stimulus display, in which the analyzing can include comparing the mfSSVEP signal at the particular frequencies to a predetermined threshold, or in relation to another mfSSVEP signal or other mfSSVEPs (e.g., including from an averaged population or individual group of mfSSVEP data with respect to that particular frequency), to determine if the signal falls below the predetermined threshold or is substantially lower with respect to a comparative mfSSVEP signal.
• the analyzing can include comparing the mfSSVEP signal at the particular frequencies to a predetermined threshold, or in relation to another mfSSVEP signal or other mfSSVEPs (e.g., including from an averaged population or individual group of mfSSVEP data with respect to that particular frequency), to determine if the signal falls below the predetermined threshold or is substantially lower with respect to a
• the method can include a process 190 to determine if the presence of a visual field defect based on the quantitative assessment, e.g., if the mfSSVEP signal for a particular frequency falls below the predetermined threshold or substantially lower than the comparative signal(s) from other mfSSVEP data at that particular frequency, in which the visual field deficiency is determined to be in the region of the visual stimulus display associated with the spatial location to which that frequency is mapped.
• a process 190 to determine if the presence of a visual field defect based on the quantitative assessment, e.g., if the mfSSVEP signal for a particular frequency falls below the predetermined threshold or substantially lower than the comparative signal(s) from other mfSSVEP data at that particular frequency, in which the visual field deficiency is determined to be in the region of the visual stimulus display associated with the spatial location to which that frequency is mapped.
• FIG. IF shows diagrams depicting an exemplary implementation using multifocal steady-state visual-evoked potentials (mfSSVEP) for assessment of visual field defects.
• mfSSVEP multifocal steady-state visual-evoked potentials
• FIG. 2 shows images of an exemplary EEG setup used in exemplary implementations of the disclosed mfSSVEP visual field loss analysis techniques. The visual experiment was conducted inside a dark, soundproof shielded room.
• the modified 10-20 international system configuration of electrodes included 19 channels of electrodes arranged over parietal and occipital areas such as Pz, P03, POz, P04, 01, Oz, and 02.
• the EEG electrode configurations of the EEG unit 11 1 can include a single electrode placed on the head or neck of the patient, e.g., such as on head over the occipital region of the brain.
• the single electrode channel configuration can include 1 channel - Oz.
• the EEG electrode configuration of the EEG unit 1 11 can include 2 electrode channels (e.g., 2 channels - 01 and 02); or in other implementations, for example, as few as 3 channels (e.g., 3 channels - 01, 02 and Oz); or in other implementations, for example, as few as 4 channels (e.g., 4 channels - POz, 01, 02 and Oz); or or in other implementations, for example, as few as 8 channels (e.g., 8 channels - P05, P03, POz, P04, P06, 01, 02 and Oz).
• 2 electrode channels e.g., 2 channels - 01 and 02
• 3 channels e.g., 3 channels - 01, 02 and Oz
• 4 channels e.g., 4 channels - POz, 01, 02 and Oz
• 8 channels e.g., 8 channels - P05, P03, POz, P04, P06, 01, 02 and Oz.
• a layout of visual stimuli was designed to include 20 sectors in three concentric rings (e.g., subtending 6 , 15 , and 25 of the visual field). All sectors flickered concurrently at different frequencies ranging from 8 to 11.8 Hz with a frequency resolution of 0.2 Hz.
• a visual field loss (DEFICIT) condition was mimicked by replacing the 9 Hz sector (e.g., the 0-45° patch in the middle ring as shown in the diagram of FIG. IF) with a black patch, in contrast to the CONTROL condition in which all 20 sectors flickered concurrently.
• the exemplary dataset for each participant contained 100 5-s DEFICIT and CONTROL trials (e.g., 10 trials x 2 conditions x 5 sessions) for analysis.
• FIG. 3A shows data plots depicting the CONTROL-DEFICIT comparison for five participants, in which the exemplary red line of the plots represent the SSVEP frequency with the lowest signal-to- noise-ratio versus other frequencies (e.g., represented by the gray lines).
• FIG. 3B shows data plots depicting a BLOCK-CONTROL comparison in mfSSVEP profiles from a representative subject.
• the exemplary empirical results showed that four of five participants consistently exhibited a significant deterioration of the 9 Hz ssVEP amplitude in the DEFICIT condition, e.g., as compared to the CONTROL condition.
• the inconsistency from a participant (S3) was likely attributed to the absence of gaze-attentive fixation to the visual stimulus during the experiment, according to his self-report after the experiment.
• the disclosed technology includes a portable, objective mfSSVEP -based visual field assessment platform, e.g., which includes and integrates a wearable, wireless dry EEG system and a head-mounted display.
• the portable devices and systems can acquire and process measurements of reliable mfSSVEP signals that are quantitatively associated with visual field integrity of a subject.
• the exemplary platform can quantitate the integrity of monocular visual fields by the characterization of mfSSVEP signal data. For example, by integrating a lightweight, wearable, and wireless multi-channel EEG system and a head-mounted display, the disclosed portable platform can allow assessment of visual field integrity in unconstrained situations and outside clinic environment.
• FIG. 4 shows an image of an exemplary portable EEG unit 11 1 of the disclosed portable, objective mfSSVEP -based visual field assessment platform.
• Exemplary characteristics of the exemplary EEG unit shown in FIG. 4 include easy-to-use and environment- free, which can avoid the burden of setting up laboratory EEG recording, enabling routine visual-field assessment or screening for visual field loss in non-clinic environments.
• Exemplary implementations using the exemplary portable devices and systems of the disclosed technology demonstrated that the strength of mfSSVEP signals is informative to serve as an objective indicator to reflect possible deficits in a monocular visual field.
• the following methods were performed.
• An exemplary wearable, wireless high-density EEG unit of the portable system platform was employed, e.g., featuring dry and non-prep electrodes and wireless telemetry to sample EEG signals at 250 Hz, as depicted in FIGS. 5A and 5B.
• FIG. 5A shows a side view image
• FIG. 5B shows a back view image of an exemplary wearable, wireless 64-channel dry EEG unit.
• the exemplary portable system can in some embodiments employ a 64-channel high-density EEG, while in other embodiments can employ a reduced number of channels to provide an optimal configuration or montage for portably detecting mfSSVEP, e.g., outside of a non-office based environment.
• the exemplary portable system can employ advanced signal processing methods, e.g., such as spatial filtering and artifact removal, to improve signal-to-noise ratio of mfSSVEP from high-density recording.
• An exemplary head-mounted display unit of the portable system platform utilized an Oculus Rift goggle (Oculus VR, Inc.) to deliver the mfSSVEP stimulation, as depicted in FIGS. 6A and 6B.
• FIG. 6A shows an image of the exemplary head-mounted display unit to present the mfSSVEP stimulation
• FIG. 6B shows a diagram of the exemplary layout of the mfSSVEP stimulation presentation.
• the exemplary head-mounted display unit provides an inexpensive solution with a good image resolution of 1280x800, and also provides a whole-eye coverage allowing a controlled environment for visual-field assessment.
• the mobility can be obtained by communicatively connecting the exemplary head-mounted display unit to one or more mobile communication devices, e.g., such as a laptop as shown in the image of FIG. 6A, or other mobile devices.
• mobile communication devices e.g., such as a laptop as shown in the image of FIG. 6A
• tablets, smartphones, or wearable computing devices can also be communicatively connected to the exemplary head- mounted display unit.
• the same layout of the mfSSVEP stimulation was used as in other exemplary implementations, e.g., including 20 sectors in three rings (e.g., subtending 6 , 15 , and 25 of the visual field) flickering at frequencies from 8 to 11.8 Hz with a frequency resolution of 0.2 Hz were used (as shown in the diagram of FIG. 6B).
• subjects can be tested under different experimental conditions, by varying testing parameters similarly to those previously described exemplary implementations.
• a visual field loss condition can be mimicked by using black patches to replace different sectors on the visual field and evaluate mfSSVEP signal loss compared to a control condition.
• the example portable system can be used for acquisition of mfSSVEP signals to obtain such data.
• exemplary techniques such as independent component analysis (ICA) and differential canonical correlation analysis can be implemented successfully for blind source separation and to enhance detectability of SSVEP signals.
• ICA independent component analysis
• differential canonical correlation analysis can be implemented successfully for blind source separation and to enhance detectability of SSVEP signals.
• Electrooculogram (EOG) methods of the disclosed technology can be utilized to successfully identify fixation losses and allow identification of unreliable mfSSVEP signals to be removed from further analyses.
• EEG Electrooculogram
• the strength of mfSSVEP in one of the five participates failed to accurately reflect the mimicked visual deficit, as depicted previously in FIG. 3 A.
• the reason may be attributed to the absence of proper gaze fixation during the examination based on the patient's self-report.
• subjects need to remain fixating on the central target location during the testing. Due to the short duration of testing trials, this can be achieved in most subjects, yet, the disclosed technology includes a mechanism to identify and exclude unreliable EEG signals produced by fixation losses. This is especially relevant in portable testing that may be performed without supervision.
• the disclosed portable mfSSVEP systems can include an EOG unit.
• the EOG unit can include two or more dry and soft electrodes to be placed proximate the outer canthus of a subject's eyes (e.g., one or more electrodes per eye) to measure corneo-retinal standing potentials, and are in communication with a signal processing and wireless communication unit of the EOG unit to process the acquired signals from the electrodes and relay the processed signals as data to the data processing unit 120 of the portable system 100.
• the electrodes of the EOG unit can be in communication with the EEG unit 1 11 or visual display unit 112 to transfer the acquired signals from the outer canthus-placed electrodes of the EOG unit to the data processing unit 120.
• the disclosed techniques can concurrently monitor subjects' electrooculogram (EOG) signals to evaluate the gaze fixation.
• EOG electrooculogram
• the electric field changes associated with eye movements e.g., such as blinks and saccades, can be monitored.
• a calibration sequence can be used at the start of recording to determine the transformation equations.
• an EOG-guided mfSSVEP analysis can be implemented to automatically exclude the EEG segments where the subjects do not gaze at the center of the stimulation.
• four prefrontal electrodes can be switched to record the EOG signals, e.g., since mfSSVEP signals are presumably weak in the prefrontal regions.
• the EOG unit includes four electrodes, two electrodes can be placed below and above the right eye and another two will be placed at the left and right outer canthus.
• the EOG unit can be used to assess the accuracy of the portable mfSSVEP system by identifying potentially unreliable EEG signals induced by loss of fixation.
• the data processing unit 120 can process the acquired signals from the EOG unit electrodes with the EEG data acquired from the EEG unit 11 1 to identify unreliable signals, which can then be removed from the analysis of visual field integrity.
• the data processing unit 120 can execute analytical techniques to provide signal source separation.
• the disclosed portable mfSSVEP systems can include an eye tracking unit to monitor losses of fixation, e.g., and can further provide a reference standard.
• the eye tracking unit can be included, integrated, and/or incorporated into the visual display unit 1 12 (e.g., exemplary head-mounted display), for example.
• Exemplary implementations can be performed to evaluate the reproducibility of measurements obtained with the exemplary portable platform in evaluating its ability to detect visual field loss in patients with glaucoma compared to healthy control subjects.
• the disclosed portable systems can provide reproducible intra- and inter-visit mfSSVEP signals. mfSSVEP signals in patients with glaucomatous visual field loss will be significantly different than those in healthy control subjects.
• measurements obtained with portable systems need to be reproducible and be able to detect visual field losses in patients with glaucoma. Good reproducibility is a fundamental requirement in order to allow detection of change over time. If a test is to be used for screening, diagnosis, and/or detection of glaucoma progression, an initial step is
• Exemplary implementations were conducted to demonstrate the reproducibility and diagnostic accuracy studies. Such implementations included participation of a group of 10 healthy and 10 glaucomatous subjects. These subjects had not been tested previously with the system. The subjects underwent five sessions of testing per visit for five different visits, spaced at intervals of approximately 1 week apart. Reproducibility measures were obtained, e.g., including coefficients of variation and intraclass correlation coefficients for the relevant measurements obtained by the portable system. For diagnostic accuracy evaluation, for example, tests of an additional sample of 20 healthy and 20 glaucomatous subjects were performed, e.g., totaling 30 subjects in each group. Glaucomatous subjects were shown to have repeatable abnormal visual field defects on SAP (SITA 24-2). For example, assessment of diagnostic accuracy was performed using receiver operating characteristic (ROC) curves. The sample size for this experiment provided 83% power to detect a minimum difference of 0.25 in ROC curve area compared to chance.
• ROC receiver operating characteristic
• a system for monitoring brain activity associated with visual field of a user includes a sensor unit to acquire electroencephalogram (EEG) signals including one or more electrodes attached to a casing wearable on the head of a user; visual display unit including a display screen to present visual stimuli to the user in a plurality of sectors of a visual field, in which the presented visual stimuli includes an optical flickering effect at a selected frequency mapped to each sector of the visual field, the visual stimuli configured to evoke multifocal steady-state visual-evoked potentials (mfSSVEP) in the EEG signals exhibited by the user acquired by the sensor unit; and a data processing unit in communication with the sensor unit and the visual display unit to analyze the acquired EEG signals and produce an assessment of the user's visual field.
• EEG electroencephalogram
• Example 2 includes the system as in example 1, in which the produced assessment of the user's visual field is a quantitative assessment that indicates if there is a presence of a visual field defect in the user's visual field.
• Example 3 includes the system as in example 1, in which the one or more electrodes of the sensor unit include dry electrodes operable to acquire the EEG signals without a conductive gel interfaced between the electrodes and the user.
• Example 4 includes the system as in example 1, in which the one or more electrodes includes a single electrode channel Oz.
• Example 5 includes the system as in example 1, in which the one or more electrodes include a plurality of the electrodes that are arranged at particular locations on the head of the subject according to the international 10-20 system.
• Example 6 includes the system as in example 1, in which the system is portable to enable the user to operate the system in the user's living environment and on a routine or continuous basis.
• Example 7 includes the system as in example 1, in which the selected frequency of the optical flickering effect for a particular sector is at a different frequency with respect to the optical flickering effect at a proximate sector or with respect to the optical flickering effects in the other sectors of the visual field.
• Example 8 includes the system as in example 7, in which the visual stimuli includes multiple and repetitive optical effects flickering at the selected frequency in the corresponding sector of the visual field of the user.
• Example 9 includes the system as in example 7, in which the visual stimuli is presented in 20 sectors in three concentric rings including subtending 6 , 15 , and 25 of the visual field.
• Example 10 includes the system as in example 7, in which the selected frequencies of the flickerings of the visual stimuli are greater than 6 Hz.
• Example 1 1 includes the system as in example 1 , further including an
• electrooculogram (EOG) unit including one or more electrodes to be placed proximate the outer canthus of each of the user's eyes to measure corneo-retinal standing potential (CRSP) signals, in which the one or more electrodes of the EOG unit are in communication with the data processing unit to process the acquired CRSP signals from the one or more electrodes to determine movements of the user's eyes.
• EOG electrooculogram
• Example 12 includes the system as in example 1, in which the visual display unit is configured to be wearable over the user's eyes for the user to view the presented visual stimuli on the display screen.
• Example 13 includes the system as in example 12, further including an eye tracking device including a camera employed in the wearable visual display unit and in communication with the data processing unit, in which the camera is operable to record images of the user's eyes.
• an eye tracking device including a camera employed in the wearable visual display unit and in communication with the data processing unit, in which the camera is operable to record images of the user's eyes.
• a method for examining a visual field of a subject includes presenting, to a subject, visual stimuli in a plurality of sectors of a visual field of a subject, in which for each sector the presented visual stimuli includes an optical flickering effect at a selected frequency; acquiring electroencephalogram (EEG) signals from one or more electrodes in contact with the head of the subject; processing the acquired EEG signals to extract multifocal steady-state visual-evoked potentials
• EEG electroencephalogram
• mfSSVEP EEG signal response to the presented visual stimuli
• Example 15 includes the method as in example 14, in which the quantitative assessment provides an indication if there is a presence of a visual field defect in the user's visual field.
• Example 16 includes the method as in example 15, in which the producing the quantitative assessment includes determining the presence of the visual field defect in a sector having a mfSSVEP signal below a predetermined threshold.
• Example 17 includes the method as in example 14, in which the visual stimuli includes multiple and repetitive optical effects flickering at the selected frequency in the corresponding sector of the visual field of the subject.
• Example 18 includes the method as in example 14, in which the one or more electrodes are included in a sensor unit wearable on the subject's head and include a single electrode channel Oz positioned over the occipital region of the head of the subject when the sensor unit is worn by the user.
• Example 19 includes the method as in example 14, in which the one or more electrodes are included in a sensor unit wearable on the subject's head such that the electrodes are arranged at particular locations on the sensing unit to be positioned on the head of the subject when the sensor unit is worn by the user.
• Example 20 includes the method as in example 14, in which the one or more electrodes include dry electrodes operable to acquire the EEG signals without a conductive gel interfaced between the electrodes and the subject.
• Example 21 includes the method as in example 14, further including monitoring movements of the user's eyes to determine instances associated with the user gazing away from the center of the visual field.
• Example 22 includes the method as in example 14, in which the monitoring the movements of the user's eyes includes using an electrooculogram (EOG) unit including one or more electrodes placed proximate the outer canthus of each of the user's eyes to measure corneo-retinal standing potential (CRSP) signals.
• EOG electrooculogram
• CRSP corneo-retinal standing potential
• Example 23 includes the method as in example 14, in which the monitoring the movements of the user's eyes includes using an eye tracking system.
• Example 24 includes the method as in example 14, in which the selected frequency of the optical flickering effect for a particular sector is presented at a different frequency with respect to the optical flickering effect at a proximate sector or with respect to the optical flickering effects in the other sectors of the visual field.
• Example 25 includes the method as in example 14, further including forming a spatial visual stimulus display having the plurality of the sectors at different spatial locations on the spatial visual stimulus display, in which, for each sector, the sector includes the optical flickering effect that changes at a designated frequency with respect to at least a proximate sector or the other sectors of the visual stimulus display.
• Example 26 includes the method as in example 14, in which the producing the quantitative assessment includes analyzing the mfSSVEP data with respect to the designated frequencies that are mapped to the sectors at the different spatial locations on the spatial visual stimulus display, in which the analyzing includes quantitatively comparing an mfSSVEP signal value at a particular frequency of the designated frequencies to a threshold value, and determining the presence of a visual field defect in the sector to which the particular frequency is mapped if the mfSSVEP signal value is less than the threshold value.
• a portable system for monitoring brain activity associated with visual field of a user includes a brain signal sensor device to acquire electroencephalogram (EEG) signals including one or more electrodes attached to a casing wearable on the head of a user; a wearable visual display unit to present visual stimuli to the user and structured to include a display screen and a casing able to secure to the head of the user, in which the wearable visual display is operable to present the visual stimuli in a plurality of sectors of the user's visual field, such that for each sector the presented visual stimuli includes an optical flickering effect at a selected frequency, and in which the visual stimuli are configured to evoke multifocal steady-state visual-evoked potentials (mfSSVEP) in the EEG signals exhibited by the user acquired by the brain signal sensor device; a data processing unit in communication with the brain signal sensor device and the wearable visual display unit to provide the visual stimuli to the wearable visual display unit and to analyze the acquired EEG signals including one or more electrodes attached to a casing wearable
• Example 28 includes the system as in example 27, in which the data processing unit is included in a computing device including a laptop or desktop computer; a mobile communication device including a smartphone, a tablet, or a wearable computing device; or a network computer system.
• Example 29 includes the system as in example 27, in which the produced assessment of the user's visual field is a quantitative assessment that indicates if there is a presence of a visual field defect in the user's visual field.
• Example 30 includes the system as in example 27, in which the one or more electrodes of the brain signal sensor device include dry electrodes operable to acquire the EEG signals without a conductive gel interfaced between the electrodes and the user.
• Example 31 includes the system as in example 27, in which the one or more electrodes includes a single electrode channel Oz.
• Example 32 includes the system as in example 27, further including an eye tracking device including a camera employed in the wearable visual display unit and in communication with the data processing unit, in which the camera is operable to record images of the user's eyes.
• an eye tracking device including a camera employed in the wearable visual display unit and in communication with the data processing unit, in which the camera is operable to record images of the user's eyes.
• Example 33 includes the system as in example 27, in which the visual stimuli includes multiple and repetitive optical effects flickering at the selected frequency in the corresponding sector of the visual field of the user, and in which the selected frequencies of the flickerings of the visual stimuli are greater than 6 Hz.
• Example 34 includes the system as in example 27, in which the wearable visual display unit is operable to form a spatial visual stimulus display on the display screen having the plurality of the sectors at different spatial locations on the spatial visual stimulus display, in which, for each sector, the sector includes the optical flickering effect that changes at a designated frequency with respect to at least a proximate sector or the other sectors of the visual stimulus display.
• Example 35 includes the system as in example 34, in which the data processing unit is operable to produce the quantitative assessment by analyzing the mfSSVEP data with respect to the designated frequencies that are mapped to the sectors at the different spatial locations on the spatial visual stimulus display, in which the analyzing includes quantitatively comparing an mfSSVEP signal value at a particular frequency of the designated frequencies to a threshold value, and determining the presence of a visual field defect in the sector to which the particular frequency is mapped if the mfSSVEP signal value is less than the threshold value.
• Implementations of the subject matter and the functional operations described in this patent document can be implemented in various systems, digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them.
• Implementations of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a tangible and non-transitory computer readable medium for execution by, or to control the operation of, data processing apparatus.
• the computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them.
• data processing apparatus encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers.
• the apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.
• a computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.
• a computer program does not necessarily correspond to a file in a file system.
• a program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code).
• a computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.
• the processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output.
• the processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).
• processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer.
• a processor will receive instructions and data from a read only memory or a random access memory or both.
• the essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data.
• a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks.
• mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks.
• a computer need not have such devices.
• Computer readable media suitable for storing computer program instructions and data include all forms of nonvolatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices.
• semiconductor memory devices e.g., EPROM, EEPROM, and flash memory devices.
• the processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

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